Automatic central-station telephone system.



No. 732,874. PATENTED JULY 7, 1903. F. MERK. AUTOMATIC CENTRAL STATION TELEPHONE SYSTEM.

APPLICATION FILED MAY 31| 1902.

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E E E E y E F. MBRK. L E 1 E AUTOMATIC CENTRAL STATION TELEPHONE SYSTEM.

E 3E APPLVIOATION FILED MAY'31. 1902.

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' T at whom it may concern:

' PATENT Patented July 'i', 1903.

Fries.

FRInnnioI-I MERK, or BERLIN, GERMANY.

AUTOMATIC CENTRAL-STATION TELEPHONE SYSTEM.

SPECIFICATION forming part of Letters Patent No. 732,874, dated July '7, 1903.

Be it known that I, FRIEDRICH MERK, engineer, a subject of the Emperor of Germany, residing at Ritterstrasse 33, Berlin, in the Empire of Germany, have invented certain. new and useful Improvements in Automatic Central-Station Telephone Systems, of which the following isa specification.

This invention consists in a modification of the well-known method of operation of automatic telephone changeover switches or cutouts, wherein such switches orcut-outs while in operation are actuated continuously and automatically by one central motor in contradistinction to other methods, whereby the switches or cut-outs are set in motion singly and step by step from the points at which telephonic messages are received by the users, of the telephones themselves.

The essential point which is characteristic of the mode of operation of a n u mber of change-over switches or cut-outs from one common center is (see, for example,German Patent No. 95,256) that a motor is maintained in operation continuously at the central exchange which operates a rotary commutator and that the several switches or cut-ontsmay at any time be con nected with such commutator singly by the persons themselves who desire to hold a conversation'onfthe telephone, after which they are so controlled by the centralor exchange motor that without any further interference on the part of the users of the telephone they perform the several operations necessary for the making or breaking of telephonic connections-such as the cutting out of the movable change-over or cut-out contacts, the testing and securing for use of the line required, the

protection of such line after it has been ongaged from disturbances, the ringing up of the person it is desired to communicate with,

g the restoration of the displaced parts of the switch to the position of rest, .&c.all in their propel-or natural sequence. The person about to engagein conversation by telephone is only required to operateonce the properswitching of the movable cut-out or change-over contacts, for which purpose before a telephonic connection is established he must move an auxiliary switch to the position required for calling up the person he wishes to communicate with, the result being that such auxiliary -der of alternation.

switch will then while the desired connection is beingmade automatically cause the lines used for telephonic communication to be switched off from the central. or exchange commutator or operating mechanism at the proper moment. a

7 Now the modification of this known method of operation to which this invention relates has for its main feature that after the connection with the exchange operating mechanism has been completed the reversing-switches or cut-outs at the exchange are actuated in such a synchronous manner that the differentop erations to be carried out, such as the operationsenumeratcd in the preceding paragraph, stand in some predetermined relation of dependency upon each other asto time or,- in other words, take place in a strictly prearranged succession of steps or periods,'and not, as hitherto, in any arbitrarily-chosen or- This change in the mode of operation of the selective switches. enables the apparatus and arrangements'employed in working telephone connections to be materially simplified, more especially Where the said switches are worked electrically with the working current proceeding from the sources of electricity at the central exchange, such current being delivered at the several points where it is to be used after the well-known method of parallel current distribution.

The electrical current may in this case be given the particular form in which it is to be used immediately on the spot where it is generated, so that the cut-out switches shunted off inlparallel from the main lines of the current-distributing system are not merely all operated direct from one central station,

but are capable of operation during the same;

periods of time from the moment they are included in the circuit. In orderto demonstrate this, the improved method of operation will hereinafter be illustrated in con nection with a small automatic telephone system adapted to be workedby means of ordinary electromagnetic change-over or cut-out switches.

In the accompanying drawings, Figure l is a general diagrammatic view of a telephone system comprising ten receivers and transmitters. Figs. 2 and 3 illustrate the connections of the central or exchange operating mechanism. Figs. 4 and 5 are detail views of each of two selective switches. Figs. 6 and 7 represent, respectively, the two receivers corresponding to the two switches shown in Figs. 4 and 5. Fig. 8 is a sectional side elevation of the call or ring-up mechanism of one of the receivers, and Fig. 9 is a diagram showing how the equilibrium of a completed telephonic connection is maintained.

First. The apparatus at each point of reception of telephonic messages, Figs; 6, 7, and 8, comprise a receiver F, which also acts as a transmitter, a polarized alarm or call bell W, a condenser C, and a cut-out hook H for the receiver to be hung on. There is further the call mechanism U, (being the auxiliary receiver switch mentioned above,) which consists of a disk 6, of hard rubber, rigidly secured in position, to which is attached an annular metal broken ring or segment 2', also the crank-handle Z, revoluble together with its shaft or spindle d, contact-spring f, and ratchet-wheel r, the last-mentioned parts tending under the action of the spiral spring 8, interposed between the said spindle d and disk 6, to turn in the direction indicated by the arrow, but being normally prevented from so doing by the anchor or pallets t. The hard-rubber disk bears a scale on its front surface the divisions of which correspond with the tooth-spaces of the escapement or ratchet-wheel r, such divisions being marked by numbers 1, 2, 3 to 10, and comprising a blank space between l and 10. The handle Z may be turned by hand in the direction of the hands of a clock to any desired number on the disk or dial e. The contact-springf constantly remains in contact with the segment t' while the handle is being so turned, but not while the said handle is in its inoperative position,'Fig. 7.

Second. The selective or cut-out switches at the exchange, Figs. 1, 4, and 5, are ordinary crank-switches, one such switch being provided for each telephonic-station line. Each station-line, and consequently the corresponding switch through which it passes, is connected in parallel with a pair of contact-pins g in each of the other switches, and

each pair of contacts g on the switch from which the call is being made is consequently connected with one of all the otherswitches. The connections to any line or station to be called are made by means of movable arms 70, which carry contacts corresponding to each pair of pins g. These studs or pins are arranged in each of the selective or out-out switches at the points of rest of the arm 70, numbered II to XI, while the telephonic lines are connected thereto in the order of the call-numbers 10, 9, 8, to 1. Rotary motion is imparted to the arm by electromagnetic action through the medium of pawls and of a toothed wheel, the requisite power being supplied by the electromagnet K. Every time that K is excited or energized the arm moves in the direction of motion of the hands of a clock by a series of steps at a uniform rate and for such a distance that at the end of every twelve successive excitations it has completed its entire circular course. Each of the cut-out or central-station switch mechanisms for making or interrupting telephonic connections furthermore includes a changeover switch, which comprises the following parts, to wit: condenser CZ), two chokecoils Da Db, a transmission-magnet M with a working contact m and a rest-contact m an electromagnetic auxiliary switch device U consisting of an electromagnet L with contacts Z to Z and in addition to this an auxiliary switch U one element of which is connected mechanically with the selective switch-- arm 7c, which controls the telephonic connections, so as to rotate therewith, and consisting of stationary contact-segments g g and a movable contact for the line 17, terminating at the arm is.

Third. The central or exchange operating mechanism, Figs. 2 and 3, consists of the batteries B, B B and E; and the commutator or switch drum T S, which is in continuous .jointly through the main conductors H L,

(indicated in the drawings by horizontal lines,) while from these the current is next delivered at the several parts singly through the branch conductors Z L, which are represented by the vertical lines. Before the cur rent reaches the points at which it is to be used it is brought to the requisite form or condition, in the main conductors of the system of "current distribution immediately in the rear of the sources of current, by the action of the switch-drum T S present case it takes the form of current impulses arranged in groups according to predetermined rates and frequencies. The switch-drum is to this end made up of the insulating switch-roller w, the four contactrings n 0 p q secured thereon, and a number of trailing springs. The four contact-rings are'notched in a manner corresponding to the diagram Fig. 2, a predetermined uniform scale divided into twenty-two units being taken as a basis in notching them. Accordingly in further referring hereinafter to the contacts made by means of the switch-drum it will be assumed that the time occupied by the switch-dru m in completing one revolution is made up of twenty-two periods of equalduration, that which is described as period 1 being the period at which the trailing or contact springs rest upon those parts of the contact-rings which are marked 1 in Fig. 2, so

that upon this assumption circuits will be closed, for example, between the conductors 7 and 14 when the roller or drum happens to be passing through its odd-numbered periods 3, 5, 7 to 21. Normally the contact variations of the switch-drum are not felt at the telephone-stations, the branch conductorsl Thus in the 2 3, &c., being disconnected save during the operation of the switches,and the condensers C O, 850., preventing their passage during a single period While a call is attempted to be made from another station in which the contacts on the arm 76 are over the pins g, corresponding to a station already connected, as will be seen from the following description of the operation of the system: Before any telephonic connection is made the handle must be set to, the call-n umber of the person it is desired to communicate with. In Fig. this 3 is supposed to be No. 6. Then while the redivision of the scale at each impulse.

quired telephonic connection is being completed the said handle is gradually released and returned to its position of rest by current impulses proceeding from the exchange and acting upon the pallets t by the excitation of the electric magnet N being moved back one The etfect of the interruption of the contact between fand t', which takes place when the crank reaches its position of rest, is transmitted to the corresponding switch at the exchange, as shown, so that in the one the proper operation of the switch at the exchange de pends upon the antecedent switching of the switchft'. Each telephone is connected to i the exchange for the purpose of making connections for the required conversations by two wires of its own, a and b, in addition to which they are all j ointlyconnected to the earth at e.

Fourth. The operation of the system is as follows: Supposing the owner of telephone No. 2, Fig. 6, wishes to put himself in communication with the owner of telephone No. 6, Fig. 7, all that is necessary todo to effect this connection is to move the crank-handle Z from its position of rest to number G on the dial. This is supposed to have been done in Fig. 6. Thereafter all the rest will be accomplished automatically by the operating mechanism at the exchange. First of all the switch of telephone No. 2, Fig. 4:, is connected with the exchange operating mechanism, Fig. 3. This connection is made during the period 1 immediately following'the adjustment of the crank-handle Z to the required position on the dial by means of a current impulse over the call'or ringing up circuit. This circuit commences at the switchdrum T S and passes through the conductors 12 and 9 over the battery, B, the main and branch conductors 1, Fig. 4, contact Z conductor 15, magnet M, choke-coil Db, conductor 1), terminal y, magnet N, contactspring f, segment i, and conductor a to terminal z, where it is closed to earth at E. During this passage of the current the magnets M and N are energized, and the magnet M by means of the contact m closes a second circuit from the battery 13" over line 13, main and branch conductors 5, contact m, conductor 16, magnet L, branch and main conductors 8 to B. This current energizes the magnet L, which, owing to the automatic completion of a new circuit from B over contion of its position of rest.

ductor 13, main and branch conductors 6, contact Zimagnet L, branch and main conductors 8 to B, remains excited up to the next time element or period 22. The operation of the change-over switch U here terminates. In the meantime magnet N, which has also been energized by the ring-up current, has caused the arm l at the call-telephone (where another station is being rung up) to travel back from number 6 to number 5. The efiect of the connection of switch No. 2 with the central or exchange operating mechanism is that the switch-drum T S at the following odd-numbered periods3, 5, 7 to 21 send out current impulses which in the first place complete the return of the arm Z in the direc- The current impulses which serve for this'return of the arm Z during the periods 3, 5, 7, 9, 11 start from the battery B going through the conductors 10 and 12 to the earth andthrough the main and branch conductors 2, contact Z, conductor 15, then exactly like the ringing-up current to the calling telephone over the conductor 6 and there again to earth. impulses,which serve to switch out the arm is, are not sent during the periods 3, 5, '7, 9, 11, because the contacts which operate or energize the magnets K and M are made at the same time at the switch-drum, and the magnet K does not commence to act until after the magnet M has ceased by reason of the contactfleaving the segment i and allowing a contact to be made at m but during the remaining odd periods 13, 15, 17, 19, and 21i1npulses are sent from B over the conductor 13, main and branch conductors 6, contact l conductors 16, contact mimagnet K, branch and main conductors 7, and conductor 14: to B. These last-named current impulses energize magnet K in each case, the result being that the arm by the time the period 22 is reached is moved to the position VI, where the couductors a and I) touch precisely the required pins, which correspond-to the line from station 6, ct and b. It will be seen that this is brought about from the fact that five of the odd-numbered periods were used inbringing the contact f back to its starting position, and therefore the number of impulses-given to the arm 7c will correspond to the complement of 5 in relation to the whole number of odd or contact periods 10, which is 5, and this brings said arm to rest on the contact VI, or those corresponding to the line from No. 6 station. If the arm Z had been set at number 5, four odd periods of the drum would have been used to return the contact 1, and its complementary number 6 would have been available to move the arm 7c to the contacts marked VII, which correspond to the line from station No. 5. When a b are disengaged or are not being used by another line, the magnet L releases its armature during the period 22, whereby connections are broken at Z Z and Z and the operation of the change-over switch is interrupted. The armature of magnet L is not again attracted at the period 22 until the arm Z is again moved, owing to the fact that the contactfhas left a segment 2', and the magnet M is therefore deenergized. The line connecting No. 6 is thus brought into circuit. At the same time the conductor a, and consequently the conductor a, is connected with B over the choke-coil Da, contact g, conductor 17, contact Z, and the branch and main conductors 3, battery B branch and main conductors 10, conductor 12 to earth, earth at station 6, call bell and wire Ct. The result is, first, that the two conductors or connecting-lines are protected from interference from other lines, and, secondly, the ringing-up circuit, over which the coil is sent, as above described, connecting the two telephones, is closed. Since this circuit is closed ,the battery B is connected by its negative pole to the earth through the switchdrum during all the odd-numbered periods, while the bell at called telephone remains in the branch circuit between the conductor a at the called station and the earth so long as the receiver remains suspended from the switch-hook H. The moment the receivers F and F are removed from their hooks at their respective telephones a circuit, as illustrated in Fig. 9, is completed, consisting of the transmitter and receiver F, conductor a, exterior contact on the arm 79, exterior con tact 9, line a, transmitter and receiver F, line b, interior contact g, interior contact on arm 7c, condenser Ob, and line b to receiver and transmitter F, enabling the conversation to be carried on. When it is desired to break 01f this connection between the two telephones, it is only necessary to connect the switch of telephone No. 2 with the exchange operating mechanism. This interruption of the connectionis effected by means of current impulses in the same manner as the connections were first formedthat is to say, by means of a circuit taking the same course as did the call or ringing up current after the user of telephone No. 2 has moved the arm Zto 1. The connection thus formed is in every detail a repetition of that first above described, except that in accordance with the movement which the arm Z has performed the arm 7c begins to be moved a little earlierthat is, it starts from the period 3 of the drum-contacts instead of from period 13. When such arm 76 has reached the position of rest XII, it remains vin that position until the period 21 is next attained, because while the arm 75 is over the contact 9 the magnet M is excited by a current proceeding from B and B and passing over the conductors 11 and 4, contact g conductor 17, contact 1*, conductor 18, magnet M, conductor 15, contact Z, and conductor 2 to battery B Not until period 21 is reached does the magnet M, being now deenergized by the break between conductors 11 and 4, permit contact to be made at m and since magnet L is not denergized until the period 22 is reached, causing a break between conductors 6 and 13, the magnet K is energized by the twentyfirst period, the current passing from battery B conductors 13 and 6, contact Z conductor 16, contact 012 magnet K, conductors 7 and 14 to B. The last connection gives a final impulse to the arm 7:), which causes it to move from the position XII to position I. At period 22 when the magnet K becomes deenergized the switch has finally come to rest until the arm Z is moved again for a fresh telephonic connection. Had the desired line a I) been in use at the time that the call was made from station 6, the bringing to rest of the switch-arm is upon the contact VI by the cutting out of the magnet L, and consequently the stopping of the intermittent action of the magnet K, which took place at the period 22 after that line was first engaged, could nothave taken place, for inasmuch as the line a at some other station-switch when engaged is connected with the positive pole of battery B by passing from a to a, the arm 70, coil Da, contact g, conductor 17, contact Z, branch and main conductors 3, there would be completed at the calling-switch during the next subsequent period 22 what is known as a test-circuit to B starting from conductor a and passing over conductor a, choke-coil Da, segment g, conductor 17, contact Z conductor 18, magnet M, conductor 15, contact l branch and main conductors 2, and battery B to B The efiect of this last circuit would be exactly the same upon the magnet M as that of the operating- 4 circuitto wit, said magnet would be energized at the end of the twenty-second period, by reason of the fact that although the contacts on the arm would engage the requisite points to energize said magnet at the end of the twenty-first period, yet the self-induction of the choke-coils Da and the inertia of the parts would retard its action until an impulse had been sent over the conductors 6, 16, and 7 at the beginning of the first period to energize the magnet K and move the switch one step. The magnet then would come into operation during said period 1 and energize magnet L to operate the switch U in the same manner as a calling-up or breaking-0E circuit and the switch-arm k of No. 2 would have been immediately returned to rest. Hence the attempt to ring up from No. 6 would have failed, without, however, disturbing No. 2 or the other person with whom No. 2 may have been conversing at that time.

What I claim, and desire to secure by Letters Patent of the United States, is-

1. In an automatic central-station system for telephones, selective switches for each station-line, means for operating said switches simultaneously and means for connecting said operating means with said switches for connecting two or more telephone-stations in pairs without interference during the same periods of time.

IIO

a ing mechanism, during the same periods of 2. In an automatic central-station system for telephones, selective switches foreach station-line, a central operating mechanism, means for connecting said switches in parallel with the central operating mechanism for performing the operations of connecting two or more telephone-stations in pairs without interference and during the same periods of time.

3. In an automatic central-station system for telephones, selective switches foreach station-line, change-over switches, a central operatin g mechanism, said change-over switches being adapted for connecting said selective switches in parallel with the central operattime whereby telephone-stations may be connected in two or more pairs without interference.

4. In an automatic central system for telephones, selective switches for each stationline,change-over switches,a central operatin g mechanism comprising a constantly-rotating drum having contact-rings of different characteristics for performing the different operations of calling up in a predetermined order, said change-over switches being adapted to connect said selective switches in parallel with the central operating mechanism without interference among pairs of telephonestations which are being connected.

5. In an automatic central system for telephones, selective switches for each stationline, change-over switches, calling-switches at each telephone-station, a central-station operating mechanism comprising contactrings of such characteristics as to operate said change-over switches, and selective switches in a predetermined order and other contactrings having successive contacts corresponding to the number of stations in the system, for operating said selective switches by the complement of the number of said contacts used in operating said calling-switches.

V 6. In an automatic central-station system for telephones, selective switches for each station-line, change-over switches, a centralstation operating mechanism comprising contact-rings of such characteristics as to operate said change-over switches and selective switches in a predetermined order and other contact-rings having successive contacts corresponding to the number of stations in the system, calling-switches at each telephonestation, comprising an escapement and a contact controlled by said escapement, whereby said contact is broken by a definite number of impulses from the contacts of the central operating mechanism and each selective switch is operated by the complementary number of said impulses.

7. In an automatic central-station system for telephones, calling-switches at each telephone-station, electrically-controlled escapements controlling said switches, selective switches and change-over switches at the central station, a central-station operating mechanism comprising constantlyrotating contact-rings of such characteristics as to operate said change-over and selective switches, in a predetermined order and during the same periods of time and other contact-rings having successive contacts corresponding to the nu mber of stations in the system, which are adapted to return the callingswitches to their normal positions bydefinite numbers-of impulses and thereafter to operate the selective switches by the complementary number of impulses.

FRIEDRICH MERK.

Witnesses:

J. TEMAN, WOLDEMAR I-IAUPT, WILLIAM MAYNER. 

